In recent years, many tea drinks packaged in containers such as cans and PET bottles have been developed and sold. The market of tea drinks, especially green tea drinks, has been expanding. Consumers have shown a growing preference for such tea drinks, and there are demands for development of a packaged green tea drink that has stronger umami and kokumi while having a moderate astringent taste, similar to a tea drink prepared by brewing high-quality tea leaves having a high total nitrogen content, such as Gyokuro and Shincha, in a teapot.
Concerning tea drinks, it is disclosed that tea leaves that contain a large amount of amino acids such as theanine are selected to produce tea drinks (Patent Document 1). There is also disclosed a method of producing essence of teas with strong umami and kokumi by causing protease to act on raw materials of teas to hydrolyze protein contained in the raw materials of teas so that amino acids, which are sources of umami, such as glutamic acid are liberated (Patent Documents 2 and 3). It is also disclosed that a tea extract is dissolved into a solvent having a high polarity and the resulting mixture is subjected to HPLC to obtain a fraction after a retention time of 25-50 minutes, which fraction can be used as a taste enhancing agent to enhance umami and kokumi of food and drinks (Patent Document 4). There are also disclosed a method for obtaining a tea drink with excellent aroma and nourishing taste, comprising extracting in water or warm water an extract from fine powdered tea, and subjecting the resulting extract solution to centrifugal separation to separate and remove large particle components originating from the fine powdered tea (Patent Document 5), and a method for obtaining a green tea drink with a rich, deep taste, comprising removing fine particles from a solution of a green tea extract to prepare a transparent solution of the green tea extract, and adding a green tea powder to the transparent solution (Patent Document 6).
Concerning macromolecular components contained in a solvent extract of tea, it is reported that tea polysaccharides obtained from a tea extract in water or hot water by use of an ultrafiltration membrane having a molecular weight cut-off of at least 400000 can prevent absorption of excess lipids from meals (Patent Document 7). Concerning water-soluble macromolecules originating from tea leaves and the like, a drink containing non-epicatechins, epicatechins and water-soluble macromolecules is proposed as a drink with reduced bitterness and astringent taste of catechins (Patent Document 8).
Glyceroglycolipid is known as a component that is produced by microorganisms (Patent Documents 9 and 10). Glyceroglycolipid is also known as a component that is contained in a wide variety of membrane fractions of plants including teas (Non-Patent Document 1). In recent years, various physiological activities of glyceroglycolipid have been found, and attempts have been made to establish a method by which glyceroglycolipid for use as bases of foods, cosmetics, and pharmaceuticals can be produced efficiently and inexpensively from safe natural products (Patent Document 11).
Patent Document 1: Japanese unexamined patent publication No. 2002-238458 (Tokukai 2002-238458)
Patent Document 2: Japanese unexamined patent publication No. 2003-144049 (Tokukai 2003-144049)
Patent Document 3: Japanese unexamined patent publication No. 2006-61125 (Tokukai 2006-61125)
Patent Document 4: Japanese unexamined patent publication No. 2005-137286 (Tokukai 2005-137286)
Patent Document 5: Japanese unexamined patent publication No. 11-276074 (Tokukaihei 11-276074)
Patent Document 6: Japanese patent No. 2981137
Patent Document 7: Japanese unexamined patent publication No. 2005476743 (Tokukai 2005476743)
Patent Document 8: Japanese patent No, 3360073
Patent Document 9: Japanese unexamined patent publication No. 2001-247593 (Tokukai 2001-247593)
Patent Document 10: Japanese patent No. 3796539
Patent Document 11: Japanese unexamined patent publication No. 2005-343814 (Tokukai 2005-343814)